This invention relates to an oil scraper piston ring which finds application particularly in internal combustion engines and which is formed of an annularly bent, cross-sectionally U-shaped sheet metal strip having slots extending alternatingly from the one and the other edge of the strip in an axial orientation. The slots are in an overlapping relationship when the metal strip is viewed circumferentially. In this manner, resilient webs are formed between the slots.
Oil scraper piston rings formed of, for example, a radially outwardly open, cross-sectionally U-shaped annularly bent metal strip are generally well known. Such piston rings engage either with radially inwardly oriented resilient tongues the base of the piston groove or they are resilient in the circumferential direction. According to a particularly advantageous prior art structure, in the metal strip there are provided substantially axially oriented slots which extend alternatingly from the one and the other strip edge and which overlap in the mid zone of the strip and thus form resilient webs. Further, radially inwardly open and circumferentially resilient metal strips are also known and are used as spreader spring rings for lamina-shaped oil scraper rings. Such spreader spring rings have, in the zone of their radially inner flank edges, axially bent support feet which serve for the radial support and often also for the axial support of the oil scrapper rings.
The problems involved in the flank deformation of the above-outlined piston ring structures are discussed in U.S. Pat. No. 2,764,458. It has been found that during the installation of such an oil scraper piston ring, a buckling of the flank segments in the axial direction upon compression of the metal strip in the circumferential direction cannot be prevented (dependent upon the stiffness of the resilient webs interconnecting the flank segments), since the resistance of the flank segments to deformation, relative to a tangential bending axis is, as a rule, substantially smaller than the deformation resistance of the resilient webs arranged perpendicularly thereto in the central zone of the metal strip. Such deformations of the ring flanks prevent a face-to-face sealing engagement of the oil scraper piston ring particularly with that side wall of the piston groove which is oriented towards the combustion chamber; as a result, the groove wear too, is also substantially increased. For this purpose, the above-noted U.S. Pat. No. 2,764,458 suggests a subsequent grinding of the oil scraper piston ring in its biased state.